Animal producers worldwide use fodder crops as an inexpensive means of feeding animals during times of forage shortfall, usually during dry summer periods or during cold winter periods. Fodder crops which can be grazed many times rather than once only have potential to lower the cost of production for many farmers.
Plants of Raphanus are used widely throughout the world for many purposes.
For example, Raphanus sativus, domestic radish is used as a vegetable for human consumption, predominantly the root but also to a lessor extent of the leaves, stems and pods.
Raphanus sativus can also be used as an oilseed crop where the seed is harvested and oil extracted. The sprouted seed may also be consumed as a sprout by humans.
Raphanus sativus is also used as a biofumigant in crop rotations to suppress pathogens such as fungal diseases, or cyst nematodes in subsequent crops particularly with Sugar Beet (Beta vulgaris) in Europe. These crops are frequently ploughed under but may also be grazed once.
Raphanus sativus may be used as a single grazing fodder crop. However, the cultivars used will usually not recover sufficiently from grazing to allow multiple grazings. Many of these cultivars are relatively early to flower, bolting with 3 months of sowing. The cultivars usually also have hairy leaves and stems which on occasion can be prickly and rejected by grazing animals.
Raphanus sativus with large bulbs may be grown for animal fodder, notably in South Africa. The cultivars used are relatively early flowering and will usually bolt to flower within 3 months of sowing.
The nutritive value of fodder radish for animal feed is known to be high and the species possesses some valuable characteristics for livestock farming. However it is clear that there are a number of features of existing cultivars which have limited its ability to provide a flexible source of grazing on farms.
The typical radish used for grazing purposes is an annual which bolts to flower very readily and rapidly. This limits its use to a single grazing before flowering as the nutritional value declines considerably at flowering. Later flowering forms would provide more flexibility on farm by allowing farmers to keep the feed until needed. This is very apparent in the related Brassica species fodder rape (Brassica napus), turnip (Brassica rapa) and kale (Brassica oleracea) where both annual and biennial forms exist. As a result in these species the biennial forms are more widely used for animal fodder than the annual forms. The delayed flowering of the biennials allows the energy they assimilate to accumulate into storage organs such as bulbs, leaf or stems. From this perspective later flowering or biennial radishes with a long growing period would be valuable for grazing over the summer, or kept until autumn and winter in a nutritious vegetative state.
When typical fodder radish crops are grazed by animals the growing point of the plant is above ground and it is damaged, limiting any regrowth. It would be valuable for a plant to have multiple low growing points to avoid grazing damage and allow maximum recovery.
The majority of traditional fodder and vegetable radish forms of Raphanus sativus are covered in short prickly hairs or trichomes and this feature can render the plant less palatable to livestock than glabrous types. Raphanus plants which lack trichomes are preferred by grazing livestock.